Une plate-forme sans fil pour electrochimique spectroscopie d'impédance

Avec l’émergence soutenue de capteurs et de dispositifs électrochimiques innovants, la spectroscopie d'impédance électrochimique est devenue l'un des outils les plus importants pour la caractérisation et la modélisation de la matière ionique et de l'interfaçage des capteurs. La capacité de détecter automatiquement, à l’aide de dispositifs électrochimiques peu couteux, les caractéristiques physiques et chimiques de la matière ionique ouvre une gamme d’application très variée pour la compréhension et l’optimisation des procédés ou interviennent les processus électrochimiques. Cette thèse décrit le développement d’une plate-forme microélectronique miniaturisée, connectée, multiplexée, et à faible coût pour la spectroscopie d'impédance diélectrique (SID) conçue pour les mesures électrochimiques in-situ et adaptée aux architectures de réseau sans fil. La plate-forme développée durant ce travail de maitrise a été testée et validée au sein d’une maille ZigBee et a été en mesure d'interfacer jusqu'à trois capteurs SID en même temps et de relayer l'information à travers le net Zigbee pour l'analyse de données et le stockage. Le système a été construit à partir de composants microélectroniques disponibles commercialement et bénéficie des avantages d'une calibration système on-the-fly qui effectue la calibration du capteur de manière aisée. Dans ce mémoire de maitrise, nous rapportons la modélisation et la caractérisation de senseurs électrochimiques de nitrate; notamment nous décrivons la conception microélectronique, la réponse d'impédance de Nyquist, la sensibilité et la précision de la mesure électrochimique, et les résultats de tests de la plate-forme pour les applications de spectroscopie d'impédance relatives à la détection du nitrate, de la détection de la qualité de l'eau, et des senseurs tactiles.The emergence of the various applications of electrochemical sensors and devices, electrochemical impedance spectroscopy became one of the most important tools for characterizing and modeling of the material and interfacing the sensors. The ability to sense in an automatic manner enables a wide variety of processes to be better understood and optimized cost-effectively. This thesis describes the development of a low-cost, miniaturized, multiplexed, and connected platform for dielectric impedance spectroscopy (DIS) designed for in-situ measurements and adapted to wireless network architectures. The platform has been tested and used as a DIS sensor node on a ZigBee mesh and was able to interface up to three DIS sensors at the same time and relay the information through the Zigbee net for data analysis and storage. The system was built from commercial microelectronics components and benefits from an on-the-fly calibration system that makes sensor calibration easy. The thesis reports characterizing and modeling of two electro-chemical devices (i.e. nitrate sensor and optically-transparent electrically-conductive glasses) and also describes the microelectronics design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the testing of the platform for in-situ dielectric impedance spectroscopy applications pertaining to fertilizer sensing, water quality sensing, and touch sensing

Développement d'un senseur électrochimique pour le dosage des nitrates en laboratoire et en pépinière forestière

Le lessivage des nitrates, la contamination de la nappe phréatique et l’eutrophisation des cours d’eau figurent parmi les enjeux planétaires qui affectent la durabilité de l’agriculture et des ressources naturelles. Ce mémoire présente le développement d’une première génération d’un nouveau senseur électrochimique pour le dosage de précisions des nitrates. Celui-ci est basé sur la spectroscopie d’impédance électrochimique d’une membrane polymérique sélective aux ions. Grâce à cette approche, un senseur compact et abordable a été produit. Par son utilisation en solutions aqueuses et en substrats de croissance saturés, il a été montré que le senseur permettait de quantifier des ajouts contrôlés de nitrates allant de 0,6 ppm à 60 ppm. La mise en application en substrat de croissance a pu être étudiée en comparaison avec des méthodes certifiées ISO 17025 visant l’analyse de ces substrats. Le senseur a aussi montré une grande versatilité par son utilisation sur divers appareils de mesure d’impédance. En plus, il a démontré une stabilité possible suite à une implantation d’un mois directement en substrat de croissance sous les variables environnementales d’une pépinière forestière. Par l’étude du spectre d’impédance du senseur en solutions pures de différentes concentrations, il a aussi été possible de proposer le circuit électrique équivalent du système, qui met en évidence deux parcours compétitifs du courant, un au coeur de la membrane et un deuxième en solution. Les résultats de ces travaux sont au coeur de deux publications scientifiques dont le manuscrit est inclus à ce mémoire. Pour finir cette étude, des suggestions seront faites pour guider l’amélioration du senseur par le développement d’une deuxième génération de celui-ci.The nitrate leaching represent a serious problematic because of ground water contamination, surface water eutrophication and soil degradation. The need for a better quantification tools to acquire data on the use of fertilizer is for great interest. This thesis presents the development of the first generation of a new electrochemical sensor for nitrate quantification based on the electrochemical impedance spectroscopy of an ion selective polymeric membrane. With this approach, a compact and cheap sensor has been produced. By its usage in aqueous solution and saturated growing media, it has been shown that the sensor allows the quantification of controlled nitrate additions from 0.6 ppm to 60 ppm. The practical application in growing media has been compared to ISO-17025 certified methods of growth medium analysis. Moreover, the sensor showed great versatility by its compatibility to many impedance measurement apparatus. Also, it has shown great stability under variables environmental condition during one month in a forest nursery. Through the impedance spectra obtained in pure solution at different concentrations, an equivalent electrical circuit has been established for the system, showing two competitive pathways for the current. The first one is going through the membrane and the second is reaching into the solution. The results of these experiments are reported in two scientific publications and included in this thesis. In conclusion, a second generation of sensor is needed to improve the quality performance regarding their selectivity and temporal stability

Recent advances in chemical sensors for soil analysis: a review

The continuously rising interest in chemical sensors' applications in environmental monitoring, for soil analysis in particular, is owed to the sufficient sensitivity and selectivity of these analytical devices, their low costs, their simple measurement setups, and the possibility to perform online and in-field analyses with them. In this review the recent advances in chemical sensors for soil analysis are summarized. The working principles of chemical sensors involved in soil analysis; their benefits and drawbacks; and select applications of both the single selective sensors and multisensor systems for assessments of main plant nutrition components, pollutants, and other important soil parameters (pH, moisture content, salinity, exhaled gases, etc.) of the past two decades with a focus on the last 5 years (from 2017 to 2021) are overviewed

Heavy metal/toxins detection using electronic tongues

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOThe growing concern for sustainability and environmental preservation has increased the demand for reliable, fast response, and low-cost devices to monitor the existence of heavy metals and toxins in water resources. An electronic tongue (e-tongue) is a multisensory array mostly based on electroanalytical methods and multivariate statistical techniques to facilitate information visualization in a qualitative and/or quantitative way. E-tongues are promising analytical devices having simple operation, fast response, low cost, easy integration with other systems (microfluidic, optical, etc) to enable miniaturization and provide a high sensitivity for measurements in complex liquid media, providing an interesting alternative to address many of the existing environmental monitoring challenges, specifically relevant emerging pollutants such as heavy metals and toxins.73119FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOSem informaçã

The EcoChip : a wireless multi-sensor platform for comprehensive environmental monitoring

This paper presents the EcoChip, a new system based on state-of-the-art electro-chemical impedance (EIS) technologies allowing the growth of single strain organisms isolated from northern habitats. This portable system is a complete and autonomous wireless platform designed to monitor and cultivate microorganisms directly sampled from their natural environment, particularly from harsh northern environments. Using 96-well plates, the EcoChip can be used in the field for realtime monitoring of bacterial growth. Manufactured with highquality electronic components, this new EIS monitoring system is designed to function at a low excitation voltage signal to avoid damaging the cultured cells. The high-precision calibration network leads to high-precision results, even in the most limiting contexts. Luminosity, humidity and temperature can also be monitored with the addition of appropriate sensors. Access to robust data storage systems and power supplies is an obvious limitation for northern research. That is why the EcoChip is equipped with a flash memory that can store data over long periods of time. To resolve the power issue, a low-power microcontroller and a power management unit control and supply all electronic building blocks. Data stored in the EcoChip’s flash memory can be transmitted through a transceiver whenever a receiver is located within the functional transmission range. In this paper, we present the measured performance of the system, along with results from laboratory tests in-vitro and from two field tests. The EcoChip has been utilized to collect bio-environemental data in the field from the northern soils and ecosystems of Kuujjuarapik and Puvirnituq, during two expeditions, in 2017 and 2018, respectively. We show that the EcoChip can effectively carry out EIS analyses over an excitation frequency ranging from 750 Hz to 10 kHz with an accuracy of 2.35%. The overall power consumption of the system was 140.4 mW in normal operating mode and 81 µW in sleep mode. The proper development of the isolated bacteria was confirmed through DNA sequencing, indicating that bacteria thrive in the EcoChip’s culture wells while the growing conditions are successfully gathered and stored

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry was held on 1–15 July 2021. The scope of this online conference was to gather experts that are well-known worldwide who are currently working in chemical sensor technologies and to provide an online forum for the presention and discussion of new results. Throughout this event, topics of interest included, but were not limited to, the following: electrochemical devices and sensors; optical chemical sensors; mass-sensitive sensors; materials for chemical sensing; nano- and micro-technologies for sensing; chemical assays and validation; chemical sensor applications; analytical methods; gas sensors and apparatuses; electronic noses; electronic tongues; microfluidic devices; lab-on-a-chip; single-molecule sensing; nanosensors; and medico-diagnostic testing

Bio-Inspired Materials for Electrochemical Sensors

Electrochemical biosensors are a rapidly growing research area that has greatly improved its specificity, accuracy, and precision in the detection of biomolecules in contemporary literature and industry alike. Typically, these systems exist in a three-electrode conformation with a working electrode functioning as the anode, a counter electrode functioning as the cathode, and a reference electrode allowing for the control of potential in the system. The method by which these sensors work is through the sharing of electrons via redox reactions with the target molecule and the working electrode or modifications on its surface. By exploiting the function of biomaterials that participate in natural substrate-binding redox phenomena, new opportunities for detecting critical molecules in complex situations can be created. In this dissertation, three distinct electrochemical biosensors were created by mimicking natural phenomena and implementing materials that directly or indirectly participate in the corresponding reactions. First, a dopamine sensor was created via a composite of lignin-derived graphene oxide and the marine algae-derived polysaccharide kappa carrageenan. Different ratios of GO, a known electrooxidizing catalyst of dopamine, with kappa carrageenan were used to create a binder-free film for dropcasting on the working electrode. It was designed on the principle of its interactions with the nervous system when injected in rats to induce analgesia, interfering with standard dopamine behavior. The system demonstrated a linear range of 1 - 250 μmol L-1 and a limit of detection of 0.14 μmol L-1 (s/n=3). In the second chapter, a sensor for the human and animal health hazard nitrite was constructed using the transition metal sulfide NiS. Transition metal sulfides are the catalytic center for nitrite oxidation to nitrate in nitrogen fixing bacteria found in the environment. This section utilized a novel electrodeposition method for creating a binderfree layer of NiS on the surface of the glassy carbon electrode. This system demonstrated a linear range of 0.04 – 1 μM, 1 – 5.3 μM and a detection limit of 0.01 μM. For the final chapter, a novel sensor was created for the cryoprotective sugar trehalose, an indicator of bacterial contamination in meat and produce without any electrochemical assay precedent. This system utilized the interactions found between alkali earth metal ions and trehalose in which the two molecules form complexes. Magnesium phthalocyanine, which is a commercially available dye, as well as synthesized magnesium tetraphenylporphyrin and calcium tetraphenylporphyrin were implemented as drop-casted coatings on the working electrode to electrodeposit trehalose on the surface and detect its oxidation via squarewave anodic stripping voltammetry in the complex media Luria-Bertani broth. The system was also used to gauge fluctuations in E. coli in broth by autoclaving the cultures and directly testing the media containing lysed bacteria. The system demonstrated a linear range of 0.25 mM – 100 mM, with magnesium mesotetraphenylporphyrin exhibiting the highest repeatability

Advances in applied electrokinetics: Treatment, by-products reuse and sensors’ system

Some of the barriers for a paradigm change on water reuse solutions are related to their maturing technology level, to the removal of emerging organic contaminants and to the availability of rapid, reliable and cost-effective monitoring tools. Thus, in this dissertation, electro-based techniques were applied to secondary effluents aiming to promote water reuse through the (i) removal of triclosan and inorganic contaminants, (ii) development and test of electronic tongue sensors that may be used as complementary monitoring tools coupled with degradation processes, and (iii) enhancing of the technology maturity level with the recovery of self-produced hydrogen and freshwater replacement in the production of construction materials. With these objectives, the main findings in this PhD project are described hereunder: (i) Electrochemical reactors are effective for degrading triclosan and its by-products. The type of electrodes is an important variable that strongly impacts the degradation efficiency, the kinetics and the by-products generated after treatment; GC/MS/MS selectivity and sensitivity allows, after operational optimization, the detection and quantification of triclosan, without the analyte derivatization, in the effluent at ng/L level, showing that standard methods should be adjusted “case-bycase”. (ii) Electronic tongues coated with organic polyelectrolyte thin films are able to distinguish at pico-molar resolution, by means of principal component analysis, between mineral water and secondary effluent matrices and discriminating triclosan at different concentrations; The coating’s stability is affected by characteristics of the water to be analysed (e.g. such as pH and elements content), rather than by the molecule to be detected; Due to this dependency, sputtering thin films, more robust and stable, should be added to the electronic tongue array; A customized electronic tongue proved be a potential complementary monitoring tool to follow the degradation pathway of the target compounds across the treatment, when coupled to a dynamic electrochemical reactor; It was possible to semi-quantify methyl-triclosan and triclosan using the array, whereas for phenolic compounds (2,4-dichlorophenol and 2,4,6-trichlorophenol) best results were obtained by using a single sensor and thinner film as coating. (iii) The remediation process by-product, hydrogen, showed, on a proof of concept level, its potential to be stored, reused or used as fuel in a proton-exchange membrane fuel cell, to generate energy; The use of electro-treated effluent showed to be sustainable for replacing freshwater in construction materials production. This replacement can provide high quality materials with features that are valued by construction materials industry, increasing the market value of the reactor developed

Laser Patterned N-doped Carbon: Preparation, Functionalization and Selective Chemical Sensors

Die kürzliche globale COVID-19-Pandemie hat deutlich gezeigt, dass hohe medizinische Kosten eine große Herausforderung für unser Gesundheitssystem darstellen. Daher besteht eine wachsende Nachfrage nach personalisierten tragbaren Geräten zur kontinuierlichen Überwachung des Gesundheitszustands von Menschen durch nicht-invasive Erfassung physiologischer Signale. Diese Dissertation fasst die Forschung zur Laserkarbonisierung als Werkzeug für die Synthese flexibler Gassensoren zusammen und präsentiert die Arbeit in vier Teilen. Der erste Teil stellt ein integriertes zweistufiges Verfahren zur Herstellung von laserstrukturiertem (Stickstoff-dotiertem) Kohlenstoff (LP-NC) ausgehend von molekularen Vorstufen vor. Der zweite Teil demonstriert die Herstellung eines flexiblen Sensors für die Kohlendioxid Erfassung basierend auf der Laserumwandlung einer Adenin-basierten Primärtinte. Die unidirektionale Energieeinwirkung kombiniert mit der tiefenabhängigen Abschwächung des Laserstrahls ergibt eine neuartige geschichtete Sensorheterostruktur mit porösen Transducer- und aktiven Sensorschichten. Dieser auf molekularen Vorläufern basierende Laserkarbonisierungsprozess ermöglicht eine selektive Modifikation der Eigenschaften von gedruckten Kohlenstoffmaterialien. Im dritten Teil wird gezeigt, dass die Imprägnierung von LP-NC mit Molybdäncarbid Nanopartikeln die Ladungsträgerdichte verändert, was wiederum die Empfindlichkeit von LP-NC gegenüber gasförmigen Analyten erhöht. Der letzte Teil erläutert, dass die Leitfähigkeit und die Oberflächeneigenschaften von LP-NC verändert werden können, indem der Originaltinte unterschiedliche Konzentrationen von Zinknitrat zugesetzt werden, um die selektiven Elemente des Sensormaterials zu verändern. Basierend auf diesen Faktoren zeigte die hergestellte LP-NC-basierte Sensorplattform in dieser Studie eine hohe Empfindlichkeit und Selektivität für verschiedene flüchtige organische Verbindungen.The recent global COVID-19 pandemic clearly displayed that the high costs of medical care on top of an aging population bring great challenges to our health systems. As a result, the demand for personalized wearable devices to continuously monitor the health status of individuals by non-invasive detection of physiological signals, thereby providing sufficient information for health monitoring and even preliminary medical diagnosis, is growing. This dissertation summarizes my research on laser-carbonization as a tool for the synthesis of functional materials for flexible gas sensors. The whole work is divided into four parts. The first part presents an integrated two-step approach starting from molecular precursor to prepare laser-patterned (nitrogen-doped) carbon (LP-NC). The second part shows the fabrication of a flexible LP-NC sensor architecture for room-temperature sensing of carbon dioxide via laser conversion of an adenine-based primary ink. By the unidirectional energy impact in conjunction with depth-dependent attenuation of the laser beam, a novel layered sensor heterostructure with a porous transducer and an active sensor layer is formed. This molecular precursor-based laser carbonization method enables the modification of printed carbon materials. In the third part, it is shown that impregnation of LP-NC with molybdenum carbide nanoparticle alters the charge carrier density, which, in turn, increases the sensitivity of LP-NC towards gaseous analytes. The last part explains that the electrical conductivity and surface properties of LP-NC can be modified by adding different concentrations of zinc nitrate into the primary ink to add selectivity elements to the sensor materials. Based on these factors, the LP-NC-based sensor platforms prepared in this study exhibited high sensitivity and selectivity for different volatile organic compounds